Condor Gold has entered into an agreement to purchase a completely new Metso Outotec SAG mill package from First Majestic Silver to serve its La India project in Nicaragua.
The purchase consideration is around $6.5 million – made up of cash and shares – with the SAG mill representing a key item of the plant required to bring La India into production, Condor said.
The SAG mill is estimated by Metso Outotec’s technical support group to have a 2,300 t/d (800,000 t/y) throughput on a sustained basis, based on the metallurgical characteristics of the ore and mineralised material at La India. Based on internal technical studies and mining dilution studies conducted by SRK Consulting, initial production at La India is expected to be 80,000-100,000 oz/y of gold.
Condor says the SAG mill and parts are 90% ready to be shipped. The 2,300 t/d capacity forms “Stage 1 of production”, with capacity to be expanded materially after two to three years of production. Its delivery reduces the order time of this key long lead item by 12 months, fast tracking La India project into production. Condor said there is the possibility of increasing throughput by 22% to 2,850 t/d by installing a 4,100 kW motor (currently a 3,330 kW motor).
Mark Child, Chairman and CEO, said: “The key message is Condor has purchased and sized the mill at 2,300 t/d, significantly shortened the mill delivery time, set a trajectory for detailed project design and an accelerated path to production. What’s more, Condor has acquired a state-of-the-art, complete new SAG mill package with warrantees, manufactured and supplied by Metso Outotec, the premier manufacturer of grinding mills and entire grinding systems for the global mining industry.”
Condor plans to commence gold production at La India in 24 months.
The SAG mill agreement has come about as First Majestic ordered a complete new SAG mill package, which, Condor says, is now superfluous to its requirements.
The SAG mill has a mill diameter of 24 ft (7.3 m) and an effective grinding length of 18.5 ft and a structural charge mass of 315 t, Condor Gold said. The structural design ball charge is 11% with a structural design load volume of 35%. Specific gravity of the material is 2.55. The structural steel liner mass is 240 t; however, with the use of lighter composite liners, the weight and corresponding power requirement can be reduced significantly to 120 t.
The complete SAG mill package manufactured and supplied by Metso Outotec includes:
- Mill shell fabricated in 8 x 90° segments;
- Mill heads cast in 4 x 90° segments with demountable trunnions;
- Ductile ring gear and carbonized pinion shaft;
- Pinion shaft assembly equipment;
- Erection cradles;
- Bracket, coupling and guard;
- Pinion bearings-2-pad polymer hydrostatic bearings;
- Transformer for the mill;
- Gear unit, steel guard and fasteners;
- Allen Bradley variable speed drive;
- Allen Bradley PLC mill local panel;
- 3,300 kW WEG SCIM (motor);
- Bearing housing;
- Torque limiter and hubs;
- Complete feed assembly. ‘Rock box’ feed chute with replaceable steel wear liners;
- Complete discharge assembly. Fabricated discharge cone (no trommel screen) with replaceable rubber wear liners;
- Discharge trunnion liner with replaceable rubber wear liners;
- Installation materials and some spares;
- Trunnion bearing;
- Hydraulic torque wrench kit;
- Liner handler; and
- Howard Marten lubrication systems (trunnion oil lube, reducer/pinion oil lube, gear spray grease lube).
It is assumed that a pebble crusher will be used in the comminution circuit to provide some additional grinding power and to manage critical size fraction material, Condor said. The SAG mill is equipped with a variable speed drive to allow the mill to operate between 1,500 t/d and 2,300 t/d. Furthermore, it is possible to increase the daily throughput by increasing the motor size, as previously indicated. The 22% boost in throughput could potentially allow gold production to increase by a similar amount, the company said.
The SRK 2017 Technical Report on La India outlined an overall process flowsheet based on a single stage SAG comminution and conventional carbon-in-leach circuit.